Local anesthetics are used in a wide variety of medical procedures. The situations where local anesthetics are used range from infiltrations to facilitate suturing lacerations in emergency rooms to prolonged use during reconstruction of hands or feet or as in tissue grafting following burns.
Local anesthetics are also used, in particular, during dental surgery, including procedures ranging from simple cavity repair to extraction and soft tissue procedures.
There are a number of local anesthetics that are used for various clinical purposes. Examples of such local anesthetics include lidocaine, bupivacaine, chloroprocaine, mepivacaine, procaine, tetracaine, and etidocaine.
These products vary in onset, duration and potency, however, the mode of action for local anesthetic drugs is essentially the same. More specifically, local anesthetics inhibit the inward flow of sodium ions in afferent small diameter C type nerve fibers, which carry certain types of pain sensations.
Local anesthetics are commonly administered using a sodium-containing buffer vehicle in order to maintain the pH and isotonicity of the anesthetic.
Unfortunately, as a result of the blockage of the sodium currents during action potential propagation caused by the local anesthetic, these anesthetic drugs may also exhibit toxicity in efferent somatic nerves, the heart, brain and other electrically excitable tissues (See Covino, B. G. "Toxicity and systemic effects of local anesthetic agents," Local Anesthetics (Strichartz, G. R. ed) Handbook of Experimental Pharmacology, Vol 81, Springer-Verlag, Berlin, 1987, pp 187-212, Garfield, J. M. and Gugino, L. "Central effects of local anesthetics." in Local Anesthetics, ibid. pp 253-284. and Munson, E. S. Mepivacaine overdose in a child Anesth. Analg. (Cleve), 52:422, 1973.) However, the potential toxicity of these anesthetic drugs is reduced when the molar dose of the local anesthetic can be minimized. (See Scott, D. B. et al..,: "Factors affecting plasma levels of lidocaine and prilocaine". Br. J. Anaesh. 44:1040, 1972.]